Embodiments of the present invention relate to methods of analysing seismic data. Merely by way of example, in some embodiments, features of a subsection of the earth may be identified, images of a subsection of the earth and/or features in the subsection of the earth may be produced and/or parameters associated with the features may be determined.
The characterisation of subsurface regions (e.g., strata or salt bodies) in a geological volume is important for identifying, accessing and managing reservoirs. The depths and orientations of such regions can be determined, for example, by seismic surveying. This is generally performed by imparting energy to the earth at one or more source locations, for example, by way of controlled explosion, mechanical input etc. Return energy is then measured at surface receiver locations at varying distances and azimuths from the source location. The travel time of energy from source to receiver, via reflections and refractions from interfaces of subsurface regions, indicates the depth and orientation of the regions. Such a method provides a seismic attribute vector field (seismic data) with various attributes (e.g., amplitude) that can then be analysed to give information regarding the geological volume.
U.S. Pat. No. 7,248,539 discloses a method for automated extraction of surface primitives from seismic data. For example, one embodiment of the method of U.S. Pat. No. 7,248,539 involves defining, typically with sub-sample precision, positions of seismic horizons through an extrema representation of a 3D seismic input volume; deriving coefficients that represent the shape of the seismic waveform in the vicinity of the extrema positions; sorting the extrema positions into groups that have similar waveform shapes by applying classification techniques with the coefficients as input attributes using unsupervised or supervised classification based on an underlying statistical class model; and extracting surface primitives as surface segments that are both spatially continuous along the extrema of the seismic volume and continuous in class index in the classification volume.
Deepwater drilling is becoming more attractive, and major discoveries have been made in deepwater, subsalt environments. When exploring subsalt hydrocarbon plays, a proper model of the salt deposits can be of great importance, both for seismic depth imaging, and to identify salt related drilling hazards.
Salt body extraction from seismic is conventionally a slow and tedious process, mainly based on manual interpretation. The lack of a suitable methodology for salt extraction can be a major bottleneck in depth migration of seismic data. More generally, it can be difficult to distinguish between spatially coherent regions of the geological volume (such as stratified regions) and spatially incoherent regions of the geological volume (such as salt bodies).